Various invisible watermarking techniques are known to those skilled in the art. Each technique generally has different advantages and satisfies different levels of robustness, security and adaptability. Many of these employ particular algorithms in determining how the pixel data of pixels in the unmarked source digital image is to be modified in order to include the particular watermark. In general, each watermark inserting technique has a corresponding watermark detecting technique. The common feature of most of these techniques is that the pixel data, or the resulting pel data, is ultimately modified in a particular way that is intended to make the modification unseen.
It is a constant endeavor to find improved techniques of placing invisible identifying marks, herein called watermarks, into a digital image. The ability to detect the presence of watermarks in a digital image is generally useful to help establish ownership, origin and authenticity, and also to discourage those who might wish to misappropriate the work. Identifying marks are also useful to give evidence of unauthorized disclosure. Heretofore watermarking methods have been concerned with inserting a watermark into a digital image after it is enlarged or reduced in size, herein called resizing, for presentation. For an inserted watermark to be subsequently detected, many image watermarking methods require that every copy of a watermarked digital image must be restored to its presentation size so a one-to-one pixel position correlation with elements in a watermarking plane can be achieved before detection is attempted. If a derived image is not resized correctly and its pixel's positions are not correlated one-to-one with elements of its appropriate watermarking plane, watermark detection will fail.